Ubuntu :: Which Used RAM Monitor Is Correct

I had to remove Xubuntu desktop and went back to pure gnome. Using 10.04 on this computer. The whole thing started to work very very slow. Anyway back in gnome I get these readings in free -m command:

Code:
total used free shared buffers cached
Mem: 228 226 2 0 10 86
-/+ buffers/cache: 129 99
Swap: 668 1 667

Then I used top command and got this:
Code:
top - 21:49:36 up 4 min, 2 users, load average: 0.86, 1.02, 0.48
Tasks: 155 total, 1 running, 154 sleeping, 0 stopped, 0 zombie
Cpu(s): 11.9%us, 4.6%sy, 0.0%ni, 83.2%id, 0.3%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 234476k total, 224660k used, 9816k free, 11596k buffers
Swap: 685048k total, 2152k used, 682896k free, 82564k cached

Finally I tried the system monitor and it said
Memory:126.6 MiB (55,3%) of 229 MiB
Swap: 2.1 MiB (0.03%) of 669 MiB

Yesterday memory was below 100. so which one is true and which one is lying? System now otherwise works fine. Quite fast actually even with more programs open.